Symptomatic ON is a rare event in patients treated with BFM-type chemotherapy with an overall 5-year cumulative incidence of 1.8%. The age group >/=10 years, and particularly adolescents >/=15 years have a significantly higher risk of developing ON.

The data suggest a hitherto unknown gender-specific impact of the -24C>T ABCC2 gene polymorphism on high-dose methotrexate pharmacokinetics. Whereas a nonfunctional MRP2 variant has been described in a patient with severe impairment of methotrexate excretion, our study is the first to suggest that a frequent ABCC2 polymorphism contributes to variability of methotrexate kinetics.

Cranial irradiation in combination with MTX therapy was associated with deficits in attention, concentration, and the ability of sequencing and processing, measured by the Kaufman factor Freedom from Distractibility. Our results support the strategy of avoiding prophylactic CNS irradiation in low risk patients.

Derivative chromosomes of 40 patients diagnosed with t(4;11) acute lymphoblastic leukemia (ALL) were analysed on the genomic DNA level. Chromosomal breakpoints were identi®ed in most cases within the known breakpoint cluster regions of the involved MLL and AF4 genes. Due to our current knowledge of the primary DNA sequences of both breakpoint cluster regions, speci®c features were identi®ed at the chromosomal fusion sites, including deletions, inversions and duplications of parental DNA sequences. After separation of all t(4;11) leukemia patients into two age classes (below and above 1 year of age), the analysis of chromosomal fusion sites revealed signi®cant di erences in the distribution of chromosomal breakpoints and led to the de®nition of two hotspot areas within the MLL breakpoint cluster region. This may point to the possibility of di erent age-linked mechanisms that were leading to t(4;11) chromosomal translocations. Oncogene (2001) 20, 2900 ± 2907.

The acute lymphoblastic leukaemia (ALL)-1 gene on human chromosome 11q23 is the site of many locally clustered chromosomal alterations associated with several types of acute leukaemias, including deletions, partial duplications and translocations. Structurally variant proteins derived from the altered gene presumably cause the malignant transformation of early haemopoietic progenitor cells. According to previously published reports, the gene consisted of at least 21 exons spread over approximately 100 kb. In this report a set of genomic fragments was isolated that represent a total of 35 exons (exons 3-37) encompassing > 95% of the protein-coding region (except exons 1 and 2) and the 3'-non-translated region of the gene. The distances between these exons were determined and a detailed restriction map was produced. The majority of the exon/intron boundaries were sequenced and an intron-phase analysis was performed. The results form the basis for a greater understanding of the translocations and other structural alterations of the gene that conserve the open reading frame and thus produce presumably oncogenic variants of the ALL-1 protein.